Elastomeric vehicle floor mats and like articles can be made by injecting a molten polymer into a mold, allowing the polymer to cool and/or crosslink, and then removing the molded article from the mold. In many cases the mold has two parts, separated by a part line. Often a first of these parts is a “core” mold block, and the other is a “cavity” mold block. The molten polymer is introduced via an orifice or gate in one of these mold blocks.
The injection of molten polymer commonly is performed at very high pressures, such as 20,000 psi. To achieve these pressures, the assembled mold is placed in a press between a stationary platen and a mobile platen. The mobile platen terminates a hydraulic ram.
In a conventional mold, the molten polymer is introduced into a gate formed in the back face of the mold block. A conduit or sprue communicates the back face of the mold block to a front face thereof, where a portion of the front face defines a portion of the surface of the article to be molded.
More recently, hot runner assemblies have been used to keep the polymer molten as it is flowing into the mold proper. A hot runner assembly has a front surface from which extend one or more nozzles. The nozzles register in respective holes or orifices of a mold block, so that a tip of the nozzle, when the mold block is assembled to the hot runner assembly, is adjacent to the mold cavity. The nozzle is thermally conductive and is equipped with electrical heating elements in order to keep the polymer molten as it flows into the mold cavity.
When a hot runner assembly is used, it has been the practice to attach a mold block to it by means of bolts which extend from the front face or parting line of the mold block, through the mold block and into the front face of the hot runner assembly. To service the nozzle(s) of the hot runner assembly, a worker has had to remove these bolts with a wrench, which is time consuming and which subjects the front face of the mold block (which in part defines the geometry of the molded article) to possible damage.
In conventional practice, when changing out one mold block for another, the hot runner assembly is removed as well. This adds to the weight of the mass being moved (which can be on the order of 20 tons). It would be desirable, therefore, to design a system in which the hot runner assembly component of the mold was left on the stationary component of the press.
It is also conventional practice to furnish the mold block or blocks with cooling channels through which water is circulated, in order to cool the molded article and to shorten molding cycle times. But these cooling channels are expensive and time-consuming to fabricate and drive up the cost of manufacturing the mold blocks. It would be advantageous to devise a system in which the cooling channels were placed elsewhere but could still provide their cooling function.